Are event handlers guaranteed to complete before AJAX callbacks are invoked?

Question

Suppose I have a event handler which makes two AJAX calls to the server:

$(\"#foo\").click(function(){ 
    $.get(\"bar\", function(){ alert(\"Hello\"); });
         


        

Answer 1

Yes, JavaScript is single threaded, so your execution will never get preempted.

Asynchronous callbacks and events work the same way; your handler for mousedown is guaranteed to finish before your handler for a mouseup, even if your mousedown handler takes 2 seconds and you let the mouse go immediately.

The same goes for an AJAX callback, it gets put into the same (kind of) queue as events waiting to be processed